1. Field of the Invention
The invention generally relates to systems and methods for fatigue testing one or more stents. More specifically, the invention relates to systems and methods for determining fatigue levels of one or more stents based on electrical resistance data associated with the one or more stents.
2. Related Art
Modern medical procedures routinely employ implants placed in a patient's vascular system to perform various therapeutic functions. As an example, stents are often inserted in an artery of a patient to maintain a flow lumen through the artery at a location that had previously been at least partially blocked. Ideally such stents, or other vascular prostheses, are able to withstand the physiological dynamics that occur within the vessel or organ in which they are emplaced. Where fracture, or other failure, of the stent, or other prosthesis, occurs removal and replacement thereof is typically necessitated. Providing a stent, or other prosthesis, of suitable strength and durability for implantation into a patient, to minimize the likelihood of failure and the associated removal and replacement thereof is thus desirable. Determining the approximate fatigue tendencies of the stent, or other prosthesis, helps accomplish the provision of a suitable stent, or other prosthesis.
Typical fatigue testers, such as in U.S. Pat. No. 4,972,721 to Conti, include motorized arrangements that drive bellows and pulse fluids into the lumen of a stent specimen to determine fatigue tendencies thereof. For example, U.S. Pat. No. 4,972,721 to Conti, discloses such an arrangement whereby fluid is pulsed or oscillated to simulate the physiological conditions the specimen would be subjected to when emplaced within the vasculature of a patient. A linear voltage-to-displacement transducer (LVDT) then measures the volume of fluid in each pulse provided by the bellows, whereas another LVDT transducer measures a change in length of the specimen during the pulsing. The suitableness of the specimen for the expected physiological parameters of a patient are then determined based on the obtained volume and length change information, which are used to calculate compliability and fatigue tendencies of a specimen based on changes in pressure, radius and length of the specimen. The number of cycles required for to render such arrangements reliable can prove cumbersome, however. Moreover, in fatigue testers where the specimen is positioned within a flexible tubing during testing, cyclic loading tends to be small. A need exists therefore for quick, easy and reliable systems and methods of determining fatigue tendencies of one or more stents by subjecting the one or more stents to larger cyclic loading strains under accelerated conditions.